Gas turbine rotor cooling



Feb. 16, 1954;

A. H. SCHUTTE 2,669,091 GAS TURBINE ROTOR COOLING Filed Jan. 13, 1951INVENTOR fl/{QWZHEIZJJSCMZ'ZZ ATTO R Patented Feb. 16, 1954 "T UNITEDSTATES- PATENT. OFFICE e 2,669,091 k 'GAs'fURBINE ROTOR COOLING AugustH.Schutte, Hastings on Hudson, N. Y. App rent January'lt, 1951, Serial No.205,866

3 Claims (Cl. 60-39.05)

This "invention relates to improvements ingas turbines and specificallyto an improved-apparatus and method of cooling the rotor'to permithigher operating efliciency. p I a v It is well-known that a majorproblem in the development of the gas turbine has bejenihdesigningrotor'bladirig which wouldwithstand the high temperatures requiredfor'lgood efliciency underthe severe stresses existing in service. It iswell. knowntoo, that relatively small gas temperature increases, in theorder of a few hundred degrees, for example, will materially raise cycleefficiency. Nevertheless in spite of the fact that higher and highertemperature alloys have been developed" and costly production methodsadopted, service temperatures are stilllimited by these factors andmaintenance problems are severe.

It is the object of this invention to provide a novel meanslfor coolingthe rotor ,blading of gas turbines so that/standard materials ofconstruetion; and methods ofmanufacture may be safely used at operatingtemperatures far in excess of thosepresently possible. I V, a v

This is basedon my prior discovery that the quenching or coolingo f veryhot gases by direct contact with atomized water droplets is surprisinglydifiicult. With hot gas temperatures of the order of 1200 to 130 1 andwith short contact time between the atomized'water droplets and the gas,I found that the water had to -be dispersed to an impossible andactually invisible fineness in order to be completely vaporized at the"end of the path of travel with a time interval of the order of 0.25second. I also found that metal surfaces such as pipe linings andthermocouple wells down stream of the atomized water injection pointbecame .coated with a liquid water film and. immediately dropped togatemperature corresponding to the water boiling point.

I propose that advantage be taken of this phenomenon to cool the firststage rotors of a hot gas turbine by injection or atomization of a smallamount of water into the gases at a point between the combustion zoneand the rotor. In this way a small portion of the water would bevaporized by the hot gases prior to contact with the rotor and theremainder of the water would wet the rotor blades; as long as the totalwater quantity was greater than the heat pickup by radiation andconvection by the cooled rotor.

I find that the amount of water required is comparatively small and willhave no appreciable cooling eiiect on the gases themselves. Thus the gastemperature can be materially increased and the exposed metal surfacewill have a temperature below that of boiling water. v

Further features of my invention will appear from the followingdisclosure of a preferred 'form of embodiment thereof taken inconnection with the attached drawing which is a central longitudinalsection diagrammatically. showing the parts of a gas turbine. r

In accordancewith the preferred form of embodiment of my invention, thegasturbinegen- .erally shown at H! is provided with a typical air intake[2, and compressor l4 whereby the air' is compressed to the desiredamount and delivered to the combustion chambers l6. Fuel'i'sconvenfiently supplied to the combustion chambers :16 by any suitablemeans such as the fuel line]!!! and in accordance with prior practicethejproducts of combustion are partially cooled withsecondary air anddischarged throughflthe. turbine 20 which drives the compressor [4through the shaft 22. The products. of combustion thenpdisr chargethrough the exhaust outlet 24. I 1 I, I

The principal feature of my invention relates to the application ofnon-combustible liquidsuch as water in finely dispersed. dropletorfparticle form to the rotor'an'd stator blades ofthe turbine 20. Thismay be conveniently, accomplished Y by a series of peripherallyspacedjets 26 inthe form of spray nozzles placed within the combustion.chamber whereby the liquid is discharged into the gas stream and againstthe turbine blades. The film formed on the blades wets the blades andthus keeps themv at a temperature below the boiling point of theliquid... 7 1

. .This mechanism is quantitativelyanalyzed as follows: y

In the case of a spherical water particle, at a temperature T2 inside aclosed chamber which is ata temperature T1, if the chambereinteriorgis ablack body, the'net rate at which'the particle of water receives rediantenergy is 1 water SdV where S is the density of water.

Therefore, dq=Ls dr where L is the latent heat of water at temperatureT2. It follows that the decrease in radius of the water particle iswhere For the 'case 'where 'the chamber "temperature T1 is 1600 R, T2is-2 20 F. and the time is 0.1 second; the radial shrinkage of theparticle is only 0.000143" or 3.6 microns. It follows that a very finemist of atomized water of 60 microns particle size would only be to1'5%vaporized in a 0.1 second travel with the1 6'00 F. hot-;gases prior toreaching the rotor. Liquid particles having an approximatesize"6f"60"to'lOWmicrons may be used.

The water mist will wet the rotor if the total water quantityissufficient .to provide a heat of evaporation equal to orgreater thanthe heat pickup by the wetted rotor surfaces. This heat pickup persquare foot of totalrotor surface by radiation willbe 1. The method ofincreasing the'efiiciency'and output horsepower fof'a gas turbinewhichcom prises introducing the motive lgas tothe turbine at a temperaturesubstantially inexcess' of a safe operating temperature for the"statoran'jd rotor blades of said turbine and "simultaneously" sprayingwater into'the gasstrea'm adja 'centthe turbine inlet to'for'ma'waterfilm'onthe rotor and stator blades, said waiterbeing in'afinely'dispersed condition having anapproxirriat'esize of 60 to 100microns'when' it leavesthespray'no'zsle and sprayed in amountsinsufficient to materially lower the gas'temperature in 'the'timethe gaspasses to the bladesarid in'a'mounts great enough to-keep the outside'ofthe blades wet, whereby the sensible temperature of the blades is atleast several hundred degrees Fahrenheit lower than the entering gastemperature.

2. The method of increasing the efiiciency and output horsepower of agas turbine which comprises introducing the gas to the turbine at atemperature substantially in excess of a safe operating temperature forthe stator and rotor blades of said turbine and simultaneously delp'ositing a water film on the stator and rotor blades whereby they havea sensible temperature in the order of several hundred degreesFahrenheit lower than the entering gas, said ='W8;t81' fl1m being formedby injecting the water in a particle range of to microns closely adjacent the .stator blades and following fuel combustion and ata point inthe gas travel such "that only about 10% to 15% of the water isvapori'zed by the gas prior to reaching the rotor blades.

3. Themethodflofincreasing the-.effieiency and output hors epowerof agas turbine which-comprises introducing the motive gas to the turbine ata temperature substantially in excess of a safe operating temperature"for the-stator and rotor blades of said turbine, and simultaneouslyspraying water intothe gas stream adjacent the turbine inlet closelyadjacent the statorblade's, andat a point in the gas travel Such thatonly a minor portion of thewater is vaporized .b'ythe gas prior 'toreaching the stator blades to form a fiIm of water on the rotor andstato'rbla'des, the water leaving'thespray nozzlebeing a'very fine'misto'f atomizedparticles and inamounts insu'fiicient tomateriallylower'the gas temper'a turein the-time the ga's fpasse'stoth'e'bladesfand in amounts-great enough to keep "the outside of theblades wet under operating conditions,whereby the sensible temperatureof the blades is at least several hundred degrees "Fahrenheit lower thanthe entering gas temperature to tne blades.

AUGUST 'SC'H'UTTE.

References Cited in the file of 'thispalterit UNITED STATES PATENTSNumber H "Nancie Date 1,824,893 'HOIZWQJI'th sept. 29, 1931 1,988,456'LY ShO hh Janf22f1 '935 2,078,958 'Lysholm Ma a, 193'! 2,095,991 "Lysholm 0. 0017. 19, 193'? 2,259,010 Taylor "Oct. 14, 1941 2,469,679 *Wyman10, 1949 2,551,229 Alford M2ty-1f1'951 FOREIGN. PATENTS "Number CountryrDate 7101776 France JuneQ, 1931 781,057 France Fb."];8, 1935

